Looking at your version of the link, I see a period in the middle of the word "youtube". The phrase ".com" isn't present either.

I think you somehow rearranged some things and omitted others when you copied and pasted.

Here's the easiest way to embed a video on BS.

Go to the Advanced menu instead of the "Quick reply" one when composing a post. Find the video icon in the menu above the text box (it looks like a strip of film), click on it and then paste the entire youtube address into the address bar of the pop up menu. Hit ok and there you go.